广西北海涠洲岛第四纪晚期火山碎屑流中橄榄岩包体碎块的发现及其地质意义

广西北海涠洲岛是我国面积最大的第四纪火山岩海岛,岛内出露的最新一次火山喷发产物为碧玄质岩石,它覆盖于晚更新世湖光岩组(Q3h)层状凝灰岩地层之上。在该火山岩中发现有橄榄岩包体,罕见的是,包体是以火山角砾的形式见于碧玄质火山碎屑流之中,故应是被炸碎的包体碎块,而非原始态包体。这是迄今为止较为特殊的一种橄榄岩包体产状类型,其原始态包体的岩石类型可能为方辉橄榄岩和纯橄岩。岩石结构及探针数据均表明该橄榄岩包体来自岩石圈地幔。包体的温压估算结果为960～1040℃和1.3GPa,对应的稳定深度约40km。此外,由于包体来源深度远小于其寄主碧玄质火山岩浆的来源深度(大于99km),表明涠洲岛地区第四纪火山碎屑流中的橄榄岩包体是地幔柱来源的碧玄质岩浆在上升经过岩石圈地幔约40km深度时捕获的偶然包体,并在就位前经历过炸碎。     

广西北海涠洲岛火山最后喷发活动时代

广西北海涠洲岛是我国最大的第四纪火山岩海岛。近些年来随着我国核电事业的不断发展,涠洲岛火山最后喷发时代和对区域核电厂址的潜在火山灾害,受到了国内外地学界和核电工业界的广泛关注。我们通过对涠洲岛南部地区射汽岩浆喷发的基浪堆积物的野外地质地貌考察,研究了火山喷发物的岩性特征、沉积结构和堆积规模。同时,对系统采集于不同堆积部位的喷发物样品和上覆的黄土样品进行了电子自旋共振(ESR)年代测试分析,结合前人光释光(OSL)测年结果,得出涠洲岛火山最后一次喷发的时间为晚更新世晚期至全新世早期,距今约13～33ka。     

广西北海涠洲岛（含斜阳岛）第四纪玄武质火山岩的地球化学性质及其源区特征

广西北海涠洲岛(含斜阳岛)是我国最大的第四纪火山岩海岛，岛内出露中更新世(Q2)溢流相玄武质火山岩、晚更新世(Q3)空落一沉积相沉火山碎屑岩和全新世(Q4)爆发一溢流相玄武质火山岩，其中中更新世为玄武岩，全新世多为碧玄岩或苦橄质碧玄岩。两者比较，前者相对高SiO2、低MgO；后者相对高MgO、低SiO2。在地球化学上，这些玄武质火山岩均属无Eu异常的轻稀土元素富集和无Nb异常的强不相容元素富集类型，较之原始地幔和N—MORB具较低的Th／La值(0．04～0．28)、La／Nb值(0．52～0．91)、Rb／Nb值(0．45～1．09)、^87Sr／86 Sr值(0．70352～0．70443)以及较高的eNd值( 3．2～ 5．2)。上述特征说明，晚更新世火山岩经历了以橄榄石和斜长石为主的分离结晶，全新世火山岩则代表了部分熔融形成的原生岩浆，同化混染作用对这两种岩浆演化的影响程度很低。根据微量元素和同位素示踪可知，涠洲岛地区火山岩的源区类似于洋岛，其岩浆来自更深的软流圈，且无大陆岩石圈组分的卷入。为此进一步推测，我国雷琼和北部湾地区深部存在一个从属于南海盆地地幔热柱的亚热柱，该亚热柱的活动一直持续到全新世。     

北部湾涠洲岛及斜阳岛火山地质与喷发历史研究

涠洲岛及斜阳岛是北部湾内一对姊妹火山岛，本文采用火山岩K-Ar法，火山岩中砂岩捕掳体光释光法（OSL）和贝壳^14C法分别测定了火山活动的年代，结合火山岩地质特征，将涠洲岛火山活动初步划分为早-中更新世（1．42Ma-0．49Ma）和晚更新世末期（36ka-33ka）两期。早-中更新世溢流玄武质熔岩盾造就了涠洲岛及斜阳岛，从涠洲岛横路山锅盖岭盾形火山锥溢出的熔岩流向四周漫流，形成涠洲岛中心高四周低的盾形火山地形，其晚阶段球状风化玄武岩沿涠洲岛潮间带分布。晚更新世末期涠洲岛南湾火山和斜阳岛斜阳村火山射气岩浆喷发，间有岩浆喷发，形成典型的低平火山口和巨厚基浪堆积几乎覆盖两岛，经历了海蚀作用，塑造了两岛现代地貌景观。     

广西北海涠洲岛晚更新世火山活动引起的地震同沉积变形构造

广西北海涠洲岛晚更新世湖光岩组为一套火山碎屑沉积,同期火山岩发育。在靠近火山口的地区,湖光岩组发育一系列地震成因的同沉积变形构造,包括:地震微断裂(张扭性地震微断裂、张性地震微断裂、共扼性地震微断裂和阶梯状地震微断裂)、微褶皱纹理、落石沉陷构造和砂泥岩脉。分析认为这些同沉积-变形构造是由同期火山活动引起的地震作用形成的。     

白头山碱流岩斑晶中固态包裹体成分的研究

长白山脉的主峰白头山是我国最年轻的火山之一。白头山碱性火山岩是中、晚更新世和全新世二期火山喷发的产物(刘嘉麒,1983)。第一期喷发以溢出熔岩为特征,熔岩主要是石英粗面岩、石英碱性粗面岩、碱流岩,形成了白头山火山锥的主体。全新世的喷发产物主要为浮岩和熔凝灰岩,其化学成分与碱流岩相似(郑祥身,1983)。岩石学和岩石化学资料表明,在岩浆演化的最后阶段,依次出现的是石英碱性粗面岩和碱流岩等碱性岩石(郑祥     

广西北海涠洲岛第四纪湖光岩组的风暴岩

广西北海涠洲岛第四纪湖光岩组以碎屑岩为主, 内发育渠筑型、丘状或洼状交错层理、平行层理等典型的风暴沉积构造.湖光岩组的风暴岩包括3种岩相类型: A.底部具渠筑型、内部具块状层理或递变层理的砾岩、砂砾岩或含砾砂岩; B.具丘状、洼状交错层理或平行层理的砂岩; C.具浪成交错层理的砂岩.这些岩相组合成典型的A -B -C风暴沉积序列, 它们分别代表在风暴作用期间风暴流(A)、风暴浪(B) 和正常波浪(C) 的沉积.晚更新世北海涠洲岛地区位于低纬度的浅海沉积背景下, 上更新统湖光岩组以正常浪及面之上的浅海背景粗火山碎屑和砂沉积为主.湖光岩组风暴岩的发现反映该区晚更新世位于风暴作用频繁的5°~ 2 0°的低纬度地区.风暴沉积发育于正常浪及面之上的浅海地带, 涠洲岛是一个风暴作用控制的浅海陆架.因此风暴岩对解释晚更新世北部湾的古地理和古气候具有重要意义      

浙江东部火山岩地区的地层时代和划分

通过对浙东地区地层特征与划分、同位素年龄等综合分析,结合近年来的新资料,认为该区前寒武纪地层由太古宙地壳物质再循环重熔结晶形成;芝溪头变质杂岩原岩可能由古元古界八都(岩)群与石炭系—二叠系沉积地层组成,二者共同于晚二叠世—中三叠世发生变质作用;中生代大规模火山岩浆活动主要发生在早白垩世晚期:磨石山群形成于早白垩世晚期,以大规模喷发酸性火山岩为特征;永康群、天台群中的众多地层也主要形成于早白垩世晚期,是不同火山构造盆地(洼地)喷发—沉积的同期异相堆积物或同期同物异名地层,以双峰式火山岩、"红层"为特征。     

中国火山/火山岩景观地质公园展望

本文概略介绍了中国大陆4个火山(岩)为主题的世界地质公园和16个国家地质公园,以及中国香港和中国台湾的两个地质公园.文章还介绍了这些地质公园火山岩喷发时代、火山类型、大地构造环境和火山(岩)景观特征与分类.它们的喷发时代主要为更新世-全新世、中新世、始新世和白垩纪.四个时期的火山地质公园,在不同年代火山中均具代表性与典...     

江西南部蔡坊盆地火山岩系层序与地质时代

江西中生代晚期火山岩系发育,形成了北部的峡江-广丰火山岩带和南部的三南-寻乌火山岩带.峡江-广丰火山岩带的火山岩系为一个火山旋回的产物,称为武夷群,并进一步划分为双峰岭、鹅湖岭和石溪组三个组.三南一寻乌火山岩带蔡坊盆地火山岩系也为一个火山旋回的产物,包括上、下两个岩性岩相单元:下单元以沉积岩为主夹火山岩,属火山喷发-沉积相,代表火山活动初始期的产物;上单元以火山岩为主,属火山喷发相,代表火山喷发期的产物.上单元顶部流纹岩SHRIMP锆石U-Pb年龄为(130.79±0.73)Ma,根据新的国际地层表,晚侏罗世与早白垩世之间的界线限定为(145.5±4)Ma,蔡坊盆地火山岩系的地质时代属早白垩世早期.通过岩性岩相对比,结合地层层位,蔡坊盆地火山岩系可归入峡江-广丰火山岩带的武夷群,其中下单元可归入双峰岭组、上单元可归入鹅湖岭组.蔡坊盆地火山岩系层序和地质时代的确定,可为三南-寻乌火山岩带火山系的研究提供参照标准.     

The terrestrial fauna of the Late Triassic Pant-y-ffynnon Quarry fissures,South Wales,UK and a new species of Clevosaurus (Lepidosauria: Rhynchocephalia)

Pant-y-ffynnon Quarry in South Wales yielded a rich cache of fossils in the early 1950s, including articulated specimens of new species (the small sauropodomorph dinosaur Pantydraco caducus and the crocodylomorph Terrestrisuchus gracilis), but no substantial study of the wider fauna of the Pant-y-ffynnon fissure systems has been published. Here, our overview of existing specimens, a few described but mostly undescribed, as well as freshly processed material, provides a comprehensive picture of the Pant-y-ffynnon palaeo-island of the Late Triassic. This was an island with a relatively impoverished fauna dominated by small clevosaurs (rhynchocephalians), including a new species, Clevosaurus cambrica, described here from a partially articulated specimen and isolated bones. The new species has a dental morphology that is intermediate between the Late Triassic Clevosaurus hudsoni, from Cromhall Quarry to the east, and the younger C. convallis from Pant Quarry to the west, suggesting adaptive radiation of clevosaurs in the palaeo-archipelago. The larger reptiles on the palaeo-island do not exceed 1.5?m in length, including a small carnivorous crocodylomorph, Terrestrisuchus, and a possible example of insular dwarfism in the basal dinosaur Pantydraco.     

Définition d'une limite multicritère ; stratigraphie du passage Campanien–Maastrichtien du site géologique de Tercis (Landes,SW France)Definition of a multi-criteria boundary; stratigraphy of the Campanian–Maastrichtian interval of the geological site at Tercis (Landes,SW France)

Lithostratigraphy, physicochemical stratigraphy, biostratigraphy, and geochronology of the 77–70 Ma old series bracketing the Campanian–Maastrichtian boundary have been investigated by 70 experts. For the first time, direct relationships between macro- and microfossils have been established, as well as direct and indirect relationships between chemo-physical and biostratigraphical tools. A combination of criteria for selecting the boundary level, duration estimates, uncertainties on durations and on the location of biohorizons have been considered; new chronostratigraphic units are proposed. The geological site at Tercis is accepted by the Commission on Stratigraphy as the international reference for the stratigraphy of the studied interval. To cite this article: G.S. Odin, C. R. Geoscience 334 (2002) 409–414.     

The effect of water on accessory phase solubility in subaluminous and peralkaline granitic melts

The solubilities of columbite, tantalite, wolframite, rutile, zircon and hafnon were determined as a function of the water contents in peralkaline and subaluminous granite melts. All experiments were conducted at 1035 °C and 2 kbar and the water contents of the melts ranged from nominally dry to approximately 6 wt.% H₂O. Accessory phase solubilities are not affected by the water content of the peralkaline melt. By contrast, solubilities are affected by the water content of the subaluminous melt, where the solubilities of all the accessory phases examined increase with the water content of the melt, up to 2 wt.% H₂O. At higher water contents, solubilities are nearly constant. It can be concluded that water is not an important control of accessory phase solubility, although the water content will affect diffusivities of components in the melt, thus whether or not accessory phases will be present as restite material. The solubility behaviour in the subaluminous and peralkaline melts supports previous spectroscopic studies, which have observed differences in the coordination of high field strength elements in dry vs. wet subaluminous granitic glasses, but not for peralkaline granitic glasses. Lastly, the fact that wolframite solubility increases with increasing water content in the subaluminous melt suggests that tungsten dissolved as a hexavalent species.     

Quaternary stresses revealed by calcite twinning inversion: insights from observations in the Savonnières underground quarry (eastern France)

Calcite samples were extracted both from the rock matrix and the superficial coating of a karstified fault plane of an underground quarry, located in the eastern border of the Paris basin. The karstification is dated as Quaternary. Analysis of mechanical calcite twinning reveals that only the calcite matrix has also undergone a compression trending WNW that can be attributed to the Mio-Pliocene alpine collision. Both coating and matrix have undergone a strike-slip regime with σ₁ roughly trending north–south, that could correspond to the regional present-day state of stress, a strike-slip compression rather trending NNW, modified by local phenomena. To cite this article: M. Rocher et al., C. R. Geoscience 335 (2003).     

HYDROGEOLOGY

正20141756 Chen Ruige(Mathematical College,China University of Geosciences,Beijing100083,China);Zhou Xun Numerical Simulation of Groundwater Level Fluctuation in a Coastal Confined Aquifer with Sloping Initial Groundwater Level Induced by the Tide(Geological Bulletin of China,ISSN1671-2552,CN11-4648/P,32(7),2013,p.1099-1104,6 illus.,16 refs.) Key words:confined water,groundwater level     

METAMORPHIC PETROLOGY

正20141408 Cai Jia(Institute of Geology,Chinese Academy of Geological Sciences,Beijing100037,China);Liu Fulai Petrogenesis and Metamorphic P-T Conditions of Garnet-Spinel-Biotitebearing Paragneiss in Danangou Area,Daqingshan-Wulashan Metamorphic Complex Belt(Acta Petrologica Sinica,ISSN1000-0569,CN11-1922/P,29(7),     

SERIALS

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GEOPHYSICAL EXPLORATION

正20142386An Guoying(China Aero Geophysical Survey and Remote Sensing Center for Land and Resources,Beijing 100083,China)Application of Satellite Remote Sensing in Regional Hydrogeological Investigation:Taking Cenozoic Strata in Wenquan Sheet(1∶250 000)of Karakoram Range as an Example(Geosci-     

QUATERNARY GEOLOGY & GEOMORPHOLOGY

正20141016An Chengbang(Key Laboratory of Western China’s Environmental Systems,Ministry of Education,Lanzhou University,Lanzhou 730000,China);Zhao Yongtao Lake Records during the Last Glacial Maximum from Xinjiang,NW China and Their Climatic Impli-     

PETROLEUM GEOLOGY

正20141538 Cao Qing(School of Earth Sciences and Engineering,Xi’an Petroleum University,Xi’an 710065,China);Zhao Jingzhou Characteristics and Significance of Fluid Inclusions from Majiagou Formation,Yichuan Huangling Area,Ordos Basin(Advances in Earth Science,ISSN1001-8166,CN62-1091/P,28(7),2013,p.819-828,7 illus.,3 tables,43 refs.)